seahaven-account-baseline/lib/backup-stack.ts

import * as cdk from "aws-cdk-lib";
import * as kms from "aws-cdk-lib/aws-kms";
import * as iam from "aws-cdk-lib/aws-iam";
import * as events from "aws-cdk-lib/aws-events";
import * as backup from "aws-cdk-lib/aws-backup";
import { Construct } from "constructs";

/**
 * Primary AWS Backup vault + plan for Sea Haven (account 328440206208), us-east-1.
 *
 * Closes audit finding C-7 (AWS Backup entirely unused) together with
 * backup-offsite-stack. Phase 1 ("critical data first"): protect the data
 * stores with no offsite leg today and copy each recovery point cross-region
 * to the GOVERNANCE-locked `seahaven-offsite` vault (us-west-2).
 *
 * Coexistence: this SUPPLEMENTS the existing EBS DLM snapshots and DynamoDB
 * PITR — it does not replace them. It adds the missing Copy3 (offsite) +
 * immutability leg. The DLM/PITR overlap is rationalized in a later phase.
 *
 * Selection is by explicit ARN (not tag-based) so we don't have to tag — and
 * drift — resources owned by other stacks (proposal-system, payments-dashboard).
 * Switch to tag-based selection when expanding past the phase-1 set.
 *
 * PRE-DEPLOY GATES (validate before the first scheduled run):
 *  - S3 backup requires bucket versioning. `accounting.seahaven.com` already
 *    has it (audit C-9); `seahaven-payments-csv-328440206208` and
 *    `google-workspace-seahavenind.com` must have versioning enabled first or
 *    their jobs fail silently (folds in audit H-21).
 *  - `database-1` is unencrypted (audit H-19). Cross-region copy of an
 *    unencrypted RDS recovery point may fail or land unencrypted. Smoke-test
 *    an on-demand backup of `database-1` FIRST and confirm the copy job to
 *    us-west-2 succeeds; if not, encrypt database-1 (H-19) or drop it from the
 *    copy until then.
 *  - DynamoDB PITR (H-7) is independent of this plan; enable it on the two
 *    tables for between-window point-in-time recovery.
 */
export class BackupStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    // CMK encrypting the primary (operational) vault. RETAIN + rotation.
    const vaultKey = new kms.Key(this, "PrimaryVaultKey", {
      alias: "backup-primary-vault",
      description: "Encrypts primary AWS Backup recovery points (us-east-1)",
      enableKeyRotation: true,
      removalPolicy: cdk.RemovalPolicy.RETAIN,
    });

    // The L2 BackupVault does NOT grant the backup service use of a customer
    // CMK; the default key policy only delegates to account IAM. Grant
    // backup.amazonaws.com the minimum KMS actions (incl. CreateGrant for
    // RDS/EBS recovery points) so backup jobs can write to this vault.
    vaultKey.addToResourcePolicy(
      new iam.PolicyStatement({
        sid: "AllowAwsBackupUseOfTheKey",
        principals: [new iam.ServicePrincipal("backup.amazonaws.com")],
        // Action set matches AWS's documented Backup vault-key policy; scoped
        // to this account so only this account's Backup service can use it.
        actions: [
          "kms:Decrypt",
          "kms:GenerateDataKey",
          "kms:GenerateDataKeyWithoutPlaintext",
          "kms:ReEncrypt*",
          "kms:DescribeKey",
        ],
        resources: ["*"],
        conditions: { StringEquals: { "aws:SourceAccount": this.account } },
      })
    );
    vaultKey.addToResourcePolicy(
      new iam.PolicyStatement({
        sid: "AllowAwsBackupCreateGrant",
        principals: [new iam.ServicePrincipal("backup.amazonaws.com")],
        actions: ["kms:CreateGrant"],
        resources: ["*"],
        conditions: {
          Bool: { "kms:GrantIsForAWSResource": "true" },
          StringEquals: { "aws:SourceAccount": this.account },
        },
      })
    );

    // Primary vault is intentionally NOT locked — it is the working copy; the
    // offsite vault carries the immutability guarantee.
    const primaryVault = new backup.BackupVault(this, "PrimaryVault", {
      backupVaultName: "seahaven-primary",
      encryptionKey: vaultKey,
      removalPolicy: cdk.RemovalPolicy.RETAIN,
    });

    // Cross-region copy destination, referenced by literal ARN (the offsite
    // stack is in another region; a literal ARN avoids crossRegionReferences /
    // SSM exports). Stack ordering is enforced via addDependency in bin/app.ts.
    const offsiteVault = backup.BackupVault.fromBackupVaultArn(
      this,
      "OffsiteVaultRef",
      `arn:aws:backup:us-west-2:${this.account}:backup-vault:seahaven-offsite`
    );

    // AWS Backup service role. Explicit (not auto-generated) because S3 backup
    // needs the S3-specific managed policy on top of the standard backup one.
    // Least-privilege: BACKUP + S3-backup only. Restore policies
    // (AWSBackupServiceRolePolicyForRestores / ...ForS3Restore) and
    // BackupSelection allowRestores are intentionally NOT granted — restores
    // are a deliberate, audited action and will get their own scoped role/path
    // once a restore-test process exists (cross-review F-1/F-2). A known role
    // name lets the deploy role's iam:PassRole be scoped to this exact ARN.
    // NOTE: creating this role is an IAM change → Sea Haven cross-review gate.
    const backupRole = new iam.Role(this, "BackupRole", {
      roleName: "seahaven-backup-service-role",
      assumedBy: new iam.ServicePrincipal("backup.amazonaws.com"),
      description: "AWS Backup service role (backup-only) for seahaven-primary",
      managedPolicies: [
        iam.ManagedPolicy.fromAwsManagedPolicyName(
          "service-role/AWSBackupServiceRolePolicyForBackup"
        ),
        iam.ManagedPolicy.fromAwsManagedPolicyName(
          "AWSBackupServiceRolePolicyForS3Backup"
        ),
      ],
    });

    // Daily backup → primary vault (35d), cross-region copy → offsite (90d).
    const plan = new backup.BackupPlan(this, "Plan", {
      backupPlanName: "seahaven-critical-daily",
      backupVault: primaryVault,
      backupPlanRules: [
        new backup.BackupPlanRule({
          ruleName: "daily-crr-offsite",
          backupVault: primaryVault,
          // 06:00 UTC — offset from the file-share DLM run.
          scheduleExpression: events.Schedule.cron({ hour: "6", minute: "0" }),
          startWindow: cdk.Duration.hours(1),
          completionWindow: cdk.Duration.hours(6),
          deleteAfter: cdk.Duration.days(35),
          copyActions: [
            {
              destinationBackupVault: offsiteVault,
              deleteAfter: cdk.Duration.days(90),
            },
          ],
        }),
      ],
    });

    // Phase-1 critical set, by explicit ARN (identifiers verified against the
    // live account 2026-05-29).
    plan.addSelection("CriticalResources", {
      backupSelectionName: "critical-data",
      role: backupRole,
      // allowRestores omitted (defaults false) — backup-only, see role comment.
      resources: [
        // RDS
        backup.BackupResource.fromArn(
          `arn:aws:rds:us-east-1:${this.account}:db:database-1`
        ),
        backup.BackupResource.fromArn(
          `arn:aws:rds:us-east-1:${this.account}:db:proposal-system-db`
        ),
        // DynamoDB (financial)
        backup.BackupResource.fromArn(
          `arn:aws:dynamodb:us-east-1:${this.account}:table/PaymentsDashboard`
        ),
        backup.BackupResource.fromArn(
          `arn:aws:dynamodb:us-east-1:${this.account}:table/purchase-orders`
        ),
        // S3 (single-copy critical buckets) — versioning required (see header)
        backup.BackupResource.fromArn("arn:aws:s3:::accounting.seahaven.com"),
        backup.BackupResource.fromArn(
          "arn:aws:s3:::seahaven-payments-csv-328440206208"
        ),
        backup.BackupResource.fromArn(
          "arn:aws:s3:::google-workspace-seahavenind.com"
        ),
      ],
    });

    cdk.Tags.of(this).add("Project", "account-baseline");
    cdk.Tags.of(this).add("Owner", "adam@seahavenind.com");
    cdk.Tags.of(this).add("Environment", "prod");
    cdk.Tags.of(this).add("ManagedBy", "cdk");

    new cdk.CfnOutput(this, "PrimaryVaultName", { value: "seahaven-primary" });
    new cdk.CfnOutput(this, "PrimaryVaultKmsKeyArn", { value: vaultKey.keyArn });
    new cdk.CfnOutput(this, "BackupPlanId", { value: plan.backupPlanId });
    new cdk.CfnOutput(this, "BackupRoleArn", { value: backupRole.roleArn });
  }
}